Ultra high efficiency, high temperature solar collection and storage

ABSTRACT

High-temperature solar trap collectors provide near ambient temperature solar entry surfaces and negligible thermal radiation losses by counterflowing low velocity transparent gases or liquids (fluids) to nullify internal thermal diffusion and radiative heat losses at the solar entry surface. Small steradian (sr) baffling plus wavelength-selective materials trap the entire 0.35 u to 2.7 u incoming solar spectrum and heat highly absorbing internal surfaces to high temperatures; only a small solid angle of the 2π steradians—on the order of 0.01 sr—of internal thermal radiation escapes. A nearly 100% efficient flat panel solar trapping embodiment exhibits alpha (α) absorption nearing 1.0 and radiant emission losses nearing 0.0 even at solar collection temperatures in excess of 1,000° K. Ultra high collection efficiency counterflow configurations are ideal for solar hot water, space heating, cooling, energy storage, and electric power generation applications.

This application claims the benefit of U.S. Provisional Application Ser. No. 61/851,083, entitled “Ultra High Efficiency, High Temperature Solar Collection and Storage”, Filed Mar. 1, 2013, the disclosure of which is hereby incorporated herein in its entirety by reference.

BACKGROUND OF INVENTION

Field of the Invention

The present application relates, in general, to a method and apparatus for achieving low-cost, renewable global energy utilizing an ultra efficient solar trap that is capable of meeting even centuries more of civilization's relentless 2% per year exponentially rising energy demands.

Discussion of Prior Art

Conventional easy-access, cheap energy is already depleted and unsustainable energy economic ceilings are being breached, but international prosperity can be restored by adopting a new abundant, dramatically lower cost energy source, such as clean solar energy. Solar energy, the world's largest energy resource, once harnessed in a useful form, such as high temperature thermal energy, can be readily stored and transformed into almost all other forms of energy, such as chemical energy, mechanical energy, electrical energy, and others. See chart 10 in FIG. 1 for mankind's 300-year energy consumption history and the apparent straightforward 300-year energy consumption trajectory.

Energy costs have risen from less than 1% of the global economy and are now approaching 14% of the $70 trillion world economy. The cost of energy, not energy abundance, now limits global prosperity—including fresh water, agricultural food production, manufactured products, and almost all jobs. All products and transportation are inexorably linked to energy costs and almost all jobs are inexorably linked to manufacturing and transporting all products. An entirely new, far larger, cheaper, and cleaner prime energy source is absolutely essential, unless gross human depopulation begins to occur within about one generation. Patch-work energy alternatives cannot meet the need. There is little debate that the industrial revolution was triggered by the combustion powered steam engine invention in 1712, and our energy appetite has exponentially grown since—enabling 300 years of unparalleled global prosperity. However, underpinning this long period of prosperity was abundant very low-cost energy—typically costing less than about five percent of the global economy. Rapidly rising and unsustainable energy recovery obstacles now govern the world economy, not to mention the almost totally ignored larger costs associated with air, land, and sea pollution. Energy, per se, is essentially unlimited if energy prices could be ignored. But, prices cannot be ignored. Thus, affordable energy governs life as we know it. The world urgently needs an immediate transition to a far larger, cleaner, and considerably less expensive alternative prime source of energy. Until the present invention, the world's largest energy resource—solar energy, which is 10,000 times larger than man's present energy needs—has not been either affordable or reliable. For just one example, the well-known prior art concentrating solar mirrors and photovoltaic solar panels shown at 12 and 14 in FIGS. 2 and 3, and again at 16 and 18 in FIGS. 4 and 5 are very inefficient in that the solar tracking panels cast long shadows and typically collect or harvest only about ⅓^(rd) to ¼^(th) of the available solar energy per acre.

SUMMARY OF THE INVENTION

In essence, the subject invention is a one way solar energy valve which enables entry of the entire solar spectrum into a solar trap, wherein solar energy is cumulatively absorbed and converted to exceptionally high usable temperatures, but does not allow the usual thermal radiation to escape from within. In other words, a solar trap device is provided which simulates a high temperature blackbody absorber with little to no emissive losses, similar in some ways to an astronomical black hole which grows in temperature with little escaping energy. Solar traps efficiently concentrate very high temperature thermal energy which can be densely stored and thereafter used on demand for an unlimited number of energy applications. This new very high temperature solar trapping technology can theoretically approach 100% efficiency per acre of solar collection, which exceeds by many times the surface area collection efficiency of all prior art solar technologies.

Briefly, the present invention is directed to an exceptionally high efficiency solar energy collector which incorporates an enclosure having an outermost entrance aperture to allow incoming radiation to enter the aperture. A working fluid is supplied to the enclosure at substantially ambient temperature and flows laminarly through the enclosure in a direction of flow that is substantially perpendicular to the outermost entrance aperture, whereby the incoming radiation is absorbed within the enclosure to heat the working fluid within before it exits as a very hot working fluid. At least one optical radiation mechanical and/or fluidic baffle is positioned to allow the incoming radiation to ultimately heat the exiting fluid within the enclosure but to prevent spectral radiation which is generated within the enclosure from escaping the enclosure. This ensures that the fluid will exit the enclosure as a highly heated working fluid, containing essentially all of the incident solar energy for directly powering thermal processes or for storage and later use as thermal energy on demand.

The invention further comprises a method for collecting solar energy, the method including the steps of directing the incoming solar spectrum through an entrance surface, which may be a wide or narrow aperture, into a container, and supplying a substantially ambient temperature working fluid to the container so as to have a laminar flow within the container in a direction that is parallel to the incident solar light direction. The method includes absorbing solar energy within the container to directly or indirectly heat the flowing working fluid and also preventing thermal energy within the container from exiting the container. Finally, the method includes directing the heated fluid out of the container to provide useful high temperature thermal energy.

The subject invention meets all of the high temperature, high collection efficiency, and long term reliable solar energy storage objectives of practical solar thermal energy—all at many times lower costs than prior arts. As will be illustrated herein, high temperature solar collection nearing 100% efficiency can be achieved by the subject invention—thereby leaving negligible room for all other solar technology improvements. The subject invention advocates the use of the most abundant raw materials on earth to construct low-cost solar traps and inexpensively store unlimited solar thermal energy—thereby paving a path to the lowest possible cost solar power technology. Such a combined breakthrough leaves little impetus for others to do better than the subject invention. For the first time in history, the subject invention employs essentially all of the fundamental physics energy functions to economically satisfy almost all of man's energy needs—not just electricity, space conditioning, and hot water—for centuries of exponentially rising energy demands.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing, and additional objects, features and advantages of the present invention will be understood by those of skill in the art from the following detailed descriptions of preferred embodiments when taken with the accompanying drawings, in which:

FIG. 1 is a 700 year time versus global energy consumption chart, depicting mankind's past 360 years and projected 340 years of rising energy consumption, plus a depiction of the best available estimates of conventional (“affordable”) combustion energy resources, all supporting the need for an urgent transition to a new prime energy resource that must be more than 100 times larger, less costly, safer, and far cleaner than all currently known energy resources;

FIGS. 2 and 3 diagrammatically illustrate prior art Concentrated Solar Power (CSP) parabolic Troughs and Central Tower CSP technologies, respectively, which attempted for many decades to generate and store high temperature solar energy in a cost effective way, and, thus far, have failed to become a cost competitive or a reliable energy source, and have largely depended on the exponentially rising cost of conventional energy to justify the existence of very high-cost prior solar arts;

FIGS. 4 and 5 diagrammatically illustrate prior art photovoltaic (PV) solar technologies which have also failed to become cost competitive or, especially not a reliable energy source;

FIG. 6 is a chart illustrating a short list of thermal diffusivity values of transparent and semi-transparent fluids, including selected gases and liquids at ambient temperatures as well as high operating temperatures;

FIG. 7 is an efficiency vs. operating temperature chart comparing a one-sun, flat panel, solar trap in accordance with the present invention to prior art one-sun flat panel collectors operating in less than 10° C. (winter) bright sunlight noontime conditions;

FIG. 8 is a chart illustrating the temperature-to-the-forth-power radiation obstacle of prior art solar thermal receivers, including the efficiency of one-sun and 100-sun solar concentration on absorbing hot surfaces—given that hotter surfaces naturally become more undesirable emitters;

FIG. 9 is a chart illustrating the peak oil availability per year, suggesting that known natural oil reserves are rapidly being depleted and that new conventional oil discoveries are inadequate to keep up with projected exponentially increasing demands within a few decades—the global consequences of which are ominous;

FIG. 10 is an expansion of a portion of the chart of FIG. 9, illustrating the “peak oil” problem and how diminishing oil reserves place large demands on remaining conventional energy sources, thereby displaying the extreme urgency of finding and implementing an entirely new and many times larger prime energy source, such as low-cost solar energy, which is capable of meeting the rapidly rising present 520×10¹⁵ BTU/yr (˜$9 trillion) annual global energy demand;

FIGS. 11(a) through 11(d) illustrate computer generated temperature vs. distance thermal diffusivity plots of four specific common gaseous, liquid, and solid materials at only 100° C., it being understood that diffusivity is not constant for each material and that diffusivity markedly changes with temperature and the plots dramatically change with material thickness (“X”) in accordance with equation 3;

FIG. 12 is a chart of absorption vs. wavelength properties of liquid water, illustrating the desirable spectral absorbance properties of liquids like water and liquid silicon oils, which can be used, like many other fluids, as a counterflowing selective wavelength fluid “baffle” in the present solar trap invention:

FIG. 13 is a diagrammatic depiction of a counterflowing solar trap device in accordance with the present invention, illustrating an example wherein 100 suns of narrow divergence solar energy is applied to an entry surface, with the input solar energy passing through one or more light baffles, and wherein counterflowing fluid progressively heats before exiting the enclosure and continues to flow, as a working fluid, to heat a thermal storage mass, and exits the thermal storage mass at near ambient temperatures before the fluid is returned to the solar entry surface to be reheated;

FIG. 14 illustrates computer generated thermal diffusion plots of four solar trap devices such as that illustrated in FIG. 13, each filled with various thicknesses of one of the Nitrogen, Argon, Sulferhexafluoride (SF6), and Xenon gases which laminarly counterflow perpendicularly away from the solar entry surface of the device at the approximate correct velocities indicated in order to nullify their normal thermal diffusion velocities toward the solar entry surface, thereby radiating almost no thermal energy at the entry surface, and so that the fluids can exit the respective solar trap devices at about 900° C. (1,200° K, 1,652° F.) as a hot working fluid with only one sun applied at the flat panel solar entry surface;

FIG. 15 is a diagrammatic depiction of a basic counterflowing solar trap device in accordance with an embodiment of the invention without thermal storage, to illustrate how to maintain the solar entry surface at ambient temperature and thus to produce little to no thermal radiation losses from the entry surface, and yet produce a very hot exiting working fluid;

FIG. 16 is a diagrammatic depiction of a high temperature solar trap device in accordance with a third embodiment of the invention, having a very long-term thermal storage device retrofitted to an existing high temperature steam thermoelectric power plant or, in the alternative, a city-wide space conditioning (heating/cooling) system employing potable water such as that illustrated in U.S. Pat. No. 6,688,129;

FIG. 17 is a diagrammatic depiction of a layered serpentine counterflow solar trap in accordance with the present invention, which also exhibits the essential optical and thermal properties of previously depicted counterflow configurations, but instead of fluids flowing substantially perpendicularly away from the solar input surface, the serpentine flow is substantially parallel to a solar input surface, followed by a series of parallel flows, each flow working its way father away from the incident solar surface and eventually exiting the serpentine solar trap as a very hot working fluid;

FIG. 18 is a diagrammatic depiction of a pipe-layered serpentine counterflow solar trap presenting an alternative geometry to the paneled counterflow serpentine in FIG. 17.

ADDITIONAL DETAILED PRIOR ART INFORMATION

FIGS. 2 and 3 illustrate examples of mirror type solar-thermal CSP (Concentrated Solar Power) devices as known in the prior art. Heliostated solar troughs are depicted in FIG. 2 at 12, and FIG. 3 depicts at 14 a central tower receiver in a heliostated mirror field. Note the exposed receiver thermal radiation potential as well as convection exposure in both of these prior art systems. Their net efficiency is low due to very high T⁴ thermal radiation losses, as illustrated by efficiency comparison chart 20 in FIG. 7. Curve 22 illustrates the efficiency of a one-sun, flat panel, solar trap in accordance with the invention (to be described), while curve 24 illustrates the efficiency of a typical prior art one-sun, commercially available, high quality prior art flat panel vacuum tube type solar collector (not illustrated) operating in less than 10° C. (winter) bright sunlight noontime conditions. Not shown in FIGS. 2 and 3 is the very expensive thermal energy storage technology used in the prior an, which typically costs 25% of an entire CSP power plant installation for only a few hours of storage drawdown. Thus, scaling up prior art storage to many days/weeks (e.g. ˜10-fold to only days of storage time) to achieve dependable power could easily more than double or triple the already prohibitively expensive cost of prior art solar power. It is these costly prior art heliostated mirror systems, receiver systems, storage systems, and many other problems with prior art solar, which have prevented the widespread adoption of CSP even in optimal desert locations. Similar shortcomings apply to solar dish CSP prior art technologies, not depicted.

The preferred embodiments of the subject solar trap invention that will be described below can readily exceed 1200° K collection temperatures with only one-sun applied instead of the typical 100-sun mirror concentration of the prior art, while simultaneously exhibiting exceptionally high collection efficiencies in excess of 90%. Prior solar art one-sun flat panels typically fall to near 0% collection efficiency at under 500° K (200° C.), and typical prior art mirror-concentrating solar tower receivers fall to 0% efficiencies at about 1200° K (900° C.). If the subject one-sun invention is augmented by the use of optical mirror concentration, such an embodiment would have no known upper temperature limits, even in excess of 1200° K, while still retaining high collection efficiencies, thereby illustrating more than a 10-fold to 100-fold improvement over the prior art. This latter embodiment can be better appreciated by emphasizing that radiation losses in prior art devices skyrocket by a factor of T⁴, which means that radiative losses normally rise by 16-fold each time the absolute collection temperature is doubled. The subject invention does not suffer from the usual prior art hot surface radiative losses. As will also be illustrated, collecting and storing just twice higher temperatures does not merely double the useful stored energy, but can surprisingly provide 10-fold or higher useful draw-down energy, which translates to an opportunity to slash storage costs by more than 10-fold.

FIG. 8 also illustrates the radiative loss shortcomings of prior art flat panel collectors and the very expensive prior art mirror type CSP collectors depicted in FIGS. 2 and 3. The radiative losses can be compared to the poor area-collection efficiencies of prior art Photovoltaic (PV) technologies illustrated in FIGS. 4 and 5. Prior art high-cost heliostated PV array installations are not only costly, but are also very energy-inefficient. Although laboratory rated at nearly 20% efficiency, the actual field-performance of PV systems is nearer to 12% efficiency. The underground power lines and computer-controlled circuits required for such heliostated systems are not visible in FIGS. 2 through 5. Note the large shadows 13, which force large spacing between the heliostated PV panels, similar to the spacing requirements of CSP mirror systems. Non-heliostated PV farms still cast shadows and suffer from reduced collection efficiency by not tracking the sun. All prior art PV panels run hot in the sun, and such absorbed waste heat further reduces PV efficiency. Low durability and constantly decreasing efficiencies with time require frequent PV panel replacements, which represent another long term PV cost obstacle. Macro electrical energy storage and conversion from DC to AC are still other factors which make PV uneconomical and especially unsuitable for 24/7 performance. Battery type PV energy storage is prohibitively expensive. Conversion of electrical PV energy to chemical storage fuels is inefficient, very expensive, and the recovery of such chemical energy is even more inefficient,—all of which reduces net PV efficiency and reliability. The final re-conversion of stored chemical energy back to useful power is a particularly costly and inefficient process. All of these, and other factors, cause even futuristic theoretical PV technology to be uneconomical when compared to conventional combustion fuel technologies, not to mention PV demands on scarce materials, which many believe cannot be scaled up to a global energy demand scale. An entirely new, much more efficient, and far lower cost macroscopic solar energy breakthrough is needed, such as the unbeatable ultra high efficiency solar traps described herein.

Until the advent of the present invention, all prior art solar thermal collection technologies have suffered from huge thermal radiation losses, even at very low collection temperatures. FIG. 7, described above, illustrates the severe “one sun” prior art flat panel deficiencies, depicting prior art rooftop style flat panel thermal performance in comparison to the subject invention and illustrating the dramatic thermal radiation losses of the prior art starting below 100° F. As a result of such low prior an collection temperatures and low efficiencies, much larger rooftop surface area collectors and very much larger and unaffordable storage technologies are required. As illustrated by curve 22, the solar trap device of the subject invention can collect far greater than 200° F.; in addition, it can be physically many times smaller and less costly, and can store 10-100 times more useful draw-down energy when stored at much higher temperatures. The subject invention can slash costs and improve performance by approximately 10-fold, while simultaneously achieving massive, long term, low cost energy storage. Storage, in useful forms, has always been the key to stand-alone solar reliability.

It is the very high temperature plus the very high efficiency distinction of the subject invention that differentiates it from all prior solar arts. This distinction is only possible by overcoming the formidable T⁴ infrared radiation losses from heated surfaces that are depicted by chart 30 in FIG. 8, which losses have barred prior art systems from efficiently collecting high temperature solar thermal energy. And yet, exceptionally high temperatures are a fundamental Carnot efficiency (equation 1) prerequisite of all thermal engines such as turbine thermoelectric powerplants:

$\begin{matrix} {\eta = {\frac{W}{Q_{H}} = {1 - {\frac{T_{O}}{T_{H}}.}}}} & {{eq}\mspace{14mu} 1} \end{matrix}$

Where W is the work done by the system (energy exiting the system as work),

Q_(H) is the heat put into the system (heat energy entering the system),

T_(C) is the absolute temperature of the cold sink reservoir, and

T_(H) is the absolute temperature of the hot source reservoir.

Clearly, the highest thermal efficiencies are achieved by employing the highest T_(H) source temperatures (and/or the coldest T_(C) sink temperatures such as in deep space). Exceptionally high temperatures are also a fundamental requirement of the lowest cost, highest energy-density storage technologies. Thus, prior art solar thermal collection technologies have been restricted to low Carnot efficiency devices, high cost solar collectors, and costly, short term thermal storage, and these formidable restrictions create unaffordable and unreliable solar power. As emphasized above, all of these items govern energy costs, products, jobs, and economic prosperity, not to mention the very long list of environmental consequences. FIG. 8 also provides a glimpse of the dramatic improvements possible with the subject solar trap invention.

FIG. 8 depicts the domination of T⁴ radiation effects in prior art solar systems which severely limits their collection efficiency at the desired high temperatures. For example, the best flat panel thermal collectors (0.9 emissivity), with one sun (1000 watts/m) noontime illumination, infrared-radiates 100% (1000 W/m²⁾ of its received energy at a panel temperature of only ˜404° K (104° C., 219° F.), which represents zero percent output efficiency. Therefore, typical high performance flat panels are limited to roughly 350° K (160 F) at only ˜50% efficiency. Similarly, intensely concentrated solar power from a field of solar mirrors (e.g. “100 suns” or 100,000 watts/m²) can only achieve about 60% efficiency at 900° K (600° C.), and 0% efficiency at receiver temperatures nearing only 1200° K (900° C.). Thus, thousands of costly mirrors are needed just to overcome radiation losses and are useless for producing energy. The subject solar trap invention can collect temperatures far in excess of 1200° K (900° C.) while maintaining nearly 100% collection efficiency. Also note in FIG. 8 how efficiency is severely impacted by radiation losses if a receiver front surface is allowed to rise by just 5° K (31 w/m²), 10° K (64 w/m²), 50° K (392 w/m²) and 100° K (992 w/m², almost 0% efficiency with 1-sun applied).

The total radiation intensities curve 32 in chart 30 of FIG. 8 can be calculated from equation 2 below:

P _(net) =Aσε(T ⁴ −T ₀ ⁴).  eq 2

Where, P is the total radiation is 2π steradians and across all wavelengths, in waits;

A is area of the radiating surface in m²

σ=a constant 5.67×10⁻⁸ W m⁻² K⁻⁴

ε=emissivity of the specific material (0 to 1)

T=temperature of surface

T_(o)=temperature of the environment into which the radiation is liberated.

Once energy is captured in a truly usable form, such as high temperature thermal energy, it can be directly employed as thermal energy or it can be efficiently transformed into almost any other form of energy, such as electricity or chemical energy. That fact envelopes almost 100% of civilization's energy needs such as direct conversion of high temperature thermal energy into cold refrigeration energy; direct space heating of buildings; direct high temperature industrial thermal process manufacturing; conversion of thermal energy into liquid or gaseous fuels; and direct thermoelectric power generation. Such ultra-efficient and low-cost solar energy invites the use of a wide array of thermo-chemical technologies to produce lower cost synthetic liquid or solid fuels. For example, thermal depolymerization chemical industries can mass produce lower cost synthetic liquid and solid fuels. Likewise, much lower cost hydrogen fuels, having no greenhouse footprint, can also be produced at high temperatures and saved at ambient temperatures. Of course, stored synthetic fuels often suffer gross inefficiencies when the stored energy is retrieved (usually by way of combustion processes).

The actual need for liquid fuels can be almost eliminated if the many promising superior battery technologies mature to enable 85% efficient electric vehicles instead of 20% efficient combustion based vehicles. If mass produced electric vehicles replace combustion vehicles, then the subject solar invention can also be the clean electric source for electric transportation.

Overarching man's long term energy dependence is the grim prospects of no energy wiggle room. Combustion, nuclear fission, fusion, deep geothermal, wind, tidal, and all other energy sources are simply inadequate, unsafe, polluting, environmentally destructive, and above all, too expensive. All prior solar arts have been unaffordable, despite the 10,000-fold abundance of solar energy. The present vastly improved solar technology removes all of the previous solar barriers. Sheer “abundance” of clean energy is no longer the prime objective. Cost is now the primary barrier.

Chart 40 in FIG. 1 plots energy consumption over time, and vividly illustrates that if man's relentless 2% per year energy progression is projected just 35 more years, humanity will require 2 times more energy per year; a humbling 4 times more energy per year in 70 years; an astronomical 8 times more in only 140 years, and; a staggering 400 times more energy per year in about three centuries—all relatively tiny time increments compared to man's >200,000 year evolution. According to speculating nuclear physicists, it could take three more centuries to master the ultimate energy—true nuclear matter annihilation energy—almost 1000 times more powerful than our current meager nuclear fission and fusion sciences. We can't gamble or wait 300 years, or probably even 30 years, for conventional combustion fuels to become scarce and decimate global economies. A Manhattan Project scale transition to ultra clean solar energy would be a wise and immediately deployable, safe option.

The immediate need for an urgent transition to a new much larger prime energy resource is an understatement. It is widely acknowledged that conventional affordable energy resources will be largely exhausted within as little as 52 to 56 years at our current 2% per year exponential consumption rate. Some cavalierly refute the 50 year premise with disregard to exponentially rising demands; to the soaring energy recovery costs; to the dire global environmental harm; or the severely adverse economic impacts. Clearly, starting a transition away from combustion fuels 50 years from now is too late, when it's all gone. A complete transition will likely take 50 years, if started today. The small percentage of combustible fuels that will be left for posterity, after a full transition to an alternative energy, will likely not be much. Many other products that require these precious hydrocarbon commodities might be scarce. Hydrocarbons simply should never be burned. Instead, they should be used and recycled.

Many are convinced that the above worrisome energy consequences will adversely impact international peace several decades before the world's conventional energy coffers are empty. But it would likely take several decades to transition from combustion and nuclear fuels and to preserve a meaningful fraction of our versatile finite material resources for posterity. If peace is important, it is essential that other far larger and especially less expensive, alternative energy resources be introduced immediately, not later.

It is widely acknowledged that global conventional energy costs will continue to sharply rise as the world's finite and easy-access resources dwindle. Thus, man's practical options are reduced to two: 1. either do without unaffordable/unavailable energy or, 2. find a way to capture and store vastly superior solar energy far less expensively. The first sacrificial option can reverse man's ascent. The second option can accelerate the ascent with abundant food, water, jobs, shelter, productivity, and human population, like few can imagine, and like mankind has never experienced. It can be vividly shown that about 98-99% of products, services, jobs, and survival itself, are inexorably linked to energy—and now—no longer the abundance of energy, but to the sheer cost of energy.

History (FIG. 1) shows that energy has subtly become the very foundation of almost all of our approximate $70 trillion global economy and life itself. During the past millennium, energy consumption per capita has insidiously crept up 100-fold from near zero external energy consumption (just 2,000 btu/day—24 watts averaged over 24 hours, or “one manpower” plus negligible animal power), all the way to about 200,000 btus per capita per day which equals 2,440 continuous watts.

Thus, humanity itself is now 98% dependent on about 198.000 btus per capita per day of external machine energy (˜2,440 continuous watts per person per 24 hours). Human survival or extinction has subtly become inexorably linked to non-human energy. Modern life, and more importantly, man's future, depends on it.

The above per capita approximations are readily supportable. The total theoretical net output power of 7 billion healthy adult males laboring at a maximum of 50 watts for 10 hours every day equals “only” 5×10¹⁵ btus per year (5 quads). But, the fact is that 7 billion of us actually consume 520×10¹⁵ btus per year (520 quads)—104 times more energy than humans alone can provide. Thus, a mere 5 quads of manpower alone, can only supply ˜1% of humanity's real energy dependence. 99% must be supplemented by external energy from the likes of combustion fuels, nuclear, hydro, bio, wind, and, preferably, the largest of them all—solar energy. This firmly illustrates how insidiously our external energy dependence has grown from near zero, now surpassing 99%—illustrated in FIG. 1.

To drive the above 99% energy dependence image home—envision the impacts of energy shortages. Energy-intense farming and food production, electric and water shortages, reduced transportation of people and goods, jobs, and peace, can all be decimated without energy. Human extinction is not an option, especially when there is now one hopeful solution—affordable and reliable solar energy. Emergency-scale solar energy preparations can only do good by providing massive new jobs, improving economic prosperity, saving the environment, and preserving our finite natural resources.

Cheap, easily accessible oil and gas will be the first to go. FIG. 9 is a stark summary of so called “peak oil.” Conventional cheap oil reserves are drying up, new oil discoveries are abruptly slowing, and the more costly new discoveries are rapidly increasing oil prices and crippling international economies. In 1956, M. King Hubbert, PhD, was first to accurately predict the 1978 U.S. peak oil crisis, which has since progressed to a global “peak oil” controversy. But Hubbert went on to illustrate the direct linkage of human population and “available” energy. The assumption is that he meant “affordable” energy because mere “available” energy is unlimited if there were no imposed upper price limits. Since then, unfortunately, the cost of energy has topped the energy priority list because energy costs have risen hundreds of percent higher than global inflation. Global energy is now teetering on “unaffordable” which has become completely synonymous with “unavailable” to most of the world's population. Unaffordable/unavailable have become interchangeable because both words now have identical consequences. Many assert that the continuing 2008 global economic troubles are directly linked to global energy costs which have reached about 14% ($9+ trillion) of the $70 trillion economy. Others assert that many more global economic meltdowns are likely if energy approaches 18% of the global economy (a mere 29% higher energy prices than in 2013). Regardless of the controversies, there is now a non-debatable dire need of a crisis-paced transition to an entirely new less costly, safer, cleaner, much larger, reliable energy source. Almost all of the scarcity controversies seem to neglect environmental destruction as having a dollar impact. If the countless environmental restoration cost impacts were factored in, the real prices of energy would be many times higher than quoted today.

FIG. 10 depicts a mere 25 year optimistic global energy consumption, which might not be realistically met because the vital and unknown energy price ingredient is omitted from this flawed official EIA report. In 25 years, no new mammoth low-cost energy discoveries are predicted and most predictions assert that international demands could be fierce long before 2035. An economic breaking point has either been already breached, or is very near. For example, the EIA predicts a doubling of “renewables” which is particularly flawed if “renewable” costs remain several times higher than the already high conventional energy prices. Likewise, the exceptionally high cost of current nuclear energy, coupled with frequent nuclear disasters and much higher future “safer” nuclear costs, leads to projecting much less than the doubling of nuclear energy that the EIA chart suggests. EIA optimism is unsupportable.

Improved energy efficiencies are always highly recommended but those bandaids can only modestly prolong the inevitable environmental destruction and energy depletion. The need of a historic paradigm energy transition remains inescapable—unless a dramatic human depopulation somehow becomes an acceptable option. Even then, an inescapable energy transition is still required to preserve global environments. The sooner the inescapable energy transition the better for the environment, the economy, and for peace. In all cases, energy costs still need to fall, not merely be maintained.

Civilization's future energy consumption (up to 400 times our current needs; see chart 40 in FIG. 1) can not be economically met by more inaccessible conventional energy reserves. And if history continues to be our teacher, then imagine evolving to 400 times more energy consumption during the next mere three centuries—wherein civilization is expected to consume in one day that which we presently consume in a year. The subject historic and benign solar trap invention is uniquely poised to meet many times the current geopolitical demands for many centuries, and can do so much less expensively, safely, and reliably.

Inaccurate reports of “hundreds of years” and even some extremist reports of “a thousand years” of nuclear energy reserves are simply unsupportable by the raw facts. Study after study supports a relatively abrupt end to affordable conventional energy reserves and resources. Even optimistic nuclear physicists proclaiming a “thousand years” of energy seem to completely ignore the shocking impact of a mere 2% per year exponential increase of energy demand, which destroys such optimism [e.g. a possible 400 times our current annual consumption PER YEAR in just ˜300 years]. For vivid clarity, the above most optimistic “1000 years” of conventional nuclear fuels could be consumed in just one or two years if, in the future, mankind actually does consume “hundreds of times” more energy PER YEAR (see FIG. 1). The objective facts stand in the face of unrealistic and overly optimistic nuclear physics projections, thereby leaving but one sufficiently large energy choice—reliable solar energy—which absolutely must be made many times less expensive. The subject invention can achieve those goals. In just 150 years, the probability is high that humanity will be consuming 100 times todays annual demands. Put in another way, within just 150 years, FIG. 1 predicts that man will consume, in one year, an entire century of today's demand.

Prior art solar technologies all fail on cost, efficiency, and long term storage. Typical 100-sun prior art Concentrating Solar Power (CSP) thermal solar collection technologies fail vital collection efficiency tests—roughly 60% efficient at meager 500-600° C. collection temperatures. Far worse, prior art CSP technologies typically achieve near 0% collection efficiencies (radiation losses equal to incoming solar flux) at only 900° C. (1200° K) as depicted in FIG. 4. To be vividly clear about “near 0% efficiency,” it means that thousands of very costly concentrating mirrors producing 100-sun intensities would be essentially useless and they would produce near zero net output power.

In other words, if 100-suns (100,000 watts per square meter) of solar power were concentrated on a highly absorbing 900° C. (1200° K) solar receiver surface, each square meter of hot receiver surface would radiate and lose an equal amount—100,000 watts—of longer wavelength light. Unfortunately, even 900° C. is not hot enough to achieve the lowest cost energy storage. If a hypothetical state of the art high efficiency 800° C. (1472° F.) turbine were powered by a hypothetical 900° C. solar storage source, the storage source would rapidly drop only 100° C. to below the 800° C. design turbine temperature and efficiency would suffer as the storage temperature decreases. By comparison, a much higher storage temperature, of the same physical size, could supply the same turbine design temperature and it could remain efficient many times longer. Thus, higher temperatures permit higher energy densities, physically smaller units, and can be much less expensive. FIG. 8 emphasizes the formidable radiation loss physics barriers which have plagued prior arts, and which can be soundly overcome by the subject invention.

The scientific community is much more familiar with thermal “conductivity” (k) than thermal “diffusion”, alpha (symbol “α”). Thermal conductivity is a measure of the steady state rate of heat flow in w/mK, whereas a is related to the time required for heat to propagate a specified distance. Thermal diffusion is a vital component of the subject invention and thus, a brief explanation is in order. FIG. 6 provides a few alpha (symbol “α”) values of select materials.

Thermal diffusion is mathematically defined:

∂T/∂t=(k/cp*ρ)(∂² T/∂x ²)  Eq. 3

Where: T: temperature, K

-   -   t: time, s     -   x: propagation distance, m     -   α=k/(cp·ρ): thermal diffusivity, m²/s     -   k: thermal conductivity at T, W/(m□K)     -   cp: specific heat capacity at T, J/(kg□K)     -   ρ: density at T, kg/m³

The thermal diffusion graphs in FIGS. 11(a) through 11(d) for CO₂ gas, liquid water, liquid silicone oil, and solid copper, respectively, at modest temperatures were computer plotted using equation 3. The computer program employing equation 3 was interfaced with scientific chart plotting software called Scilab 5.1 (GUI). It is not obvious to those only familiar with common thermal conductivity (k) values that thermal propagation through materials can take so much time. For example, the thermal conductivity of water (FIG. 11(b)) is about 0.6 w/mK and that of silicone oil (FIG. 11(c)) (0.04 w/mK) is about 15 times less than water. It takes about 2500 seconds for heat to propagate through 1 meter of non-convective water, but about 300 times longer (800,000 seconds) to propagate through the same thickness of silicone oil. For an extreme example of thermal diffusion, heat generated deep in the sun takes 100,000 years to propagate (diffuse) to the surface and escape as radiation. Note in the chart of FIG. 6 the large changes in the alpha (a) term in equation 3 versus temperature. Also, particularly note how thermal propagation is related to the square of the distance (“X”) in equation 3. This distance feature, and the propagation function exponentially controlled by it, is critically employed in designing counterflowing solar traps

The low thermal diffusion time property of materials enables the subject invention to overcome one of the most problematic barriers of prior art solar collection. If the working fluid in a solar collector is purposely flowed through the solar collector at the correct velocity to prevent heat from ever conductively or convectively reaching the solar entry surface, then the surface cannot heat or radiate (lose) energy. This diffusion phenomenon will be referenced in the invention section below, but it is not the only feature which enables the subject invention to reach extremely high temperatures and remain so energy efficient. Wavelength selectivity and angular geometric radiation directivity/selectivity are also features which greatly help to make the subject solar traps ultra efficient at extremely high operating temperatures. Each of the features and physics phenomena is expanded in the preferred embodiments below.

PREFERRED EMBODIMENTS OF THE INVENTION

As illustrated diagrammatically in FIG. 13, one embodiment the present invention—includes an exceptionally high efficiency solar trap or solar collector system generally shown at 50, which includes an enclosure, or container 52, having a back-most wall 54 and a front-most optically clear solar entrance aperture surface 56, to allow incoming solar radiation 58 to enter the container. The container may be generally in the form of a rectangular box, for example. A working fluid 60 such as a suitable liquid or gas, is supplied to the container by way of an inlet supply line 62, the fluid entering the container at substantially ambient temperatures and flowing through the container in a direction that is substantially perpendicular to the surface receiving the solar energy, and thus perpendicular to the solar entrance aperture surface 56. This is a laminar flow through the enclosure 50, with at least one mechanical baffle 64 allowing the fluid to flow in a direction indicated by arrows 66. Incoming radiation 58 is minimally absorbed by the working fluid 60 or by the mechanical baffles 64 within the enclosure, but maximally absorbed at the highly absorbing internal bottom surface 90—all of which heat ultimately is conductively transferred to the working fluid to achieve a high temperature before the fluid exits the solar trap at pipe 70. The highly absorbing hot bottom surface 90 radiates or emits intense and highly dispersed radiant energy in a 2π steradian (6.28 steradian) dispersion pattern backward toward the entry surface aperture 56 and counter to the fluid flow direction. At least one optical baffle 64 is positioned to allow the nearly parallel ˜0.01 steradian incoming solar radiation to travel relatively unobstructed through the fluid and baffle(s) 64 within the enclosure all the way to the highly absorbing bottom surface 90 of the enclosure. However, the highly dispersed 2π steradian nature of the emitted radiation from the hot bottom surface is almost completely obstructed by the very narrow steradian openings of the baffle(s) 64 to prevent it from reaching the entry surface of the enclosure. Thus, narrow aperture baffles absorb 2π radiant energy by multi reflection and absorption effects. The counterflowing fluid 60 conductively cools the radiantly heated baffle(s) 64. Heat at the hot back surface 90 is not just radiantly emitted toward the front aperture 56, heat energy also diffusively conducts toward the front surface 56, which if allowed to reach and heat the front surface 56, would then radiate into the environment as a very large energy loss. However, the natural slow thermal diffusion of heat through the working fluid toward the front surface 56 is completely nullified by the slow velocity of the counterflowing transparent fluid 60, which maintains the front surface 56 at ambient temperatures at all times. It should also be noted that a very slight positive counterflowing fluid pressure also completely nullifies any possibility of internal fluids convectively making it to the front entry surface 56. Thus, counterflowing fluid 60 may be referred to as a thermal diffusion and convection nullifier, while the mechanical baffle(s) 64 nullify almost all of the radiation from the hot back surface 90—the combined thermal nullification processes resulting in maintaining the frontmost surface 56 near ambient temperature, and therefore, preventing the entire solar trap from losing internal thermal energy. Clearly, the exterior non-optical walls of the solar trap enclosure 50 can be thermally insulated to almost any amount desired. As will be illustrated later, an alternate embodiment of the subject invention employs no mechanical baffles, but instead, employs at least one counterflowing fluid which exhibits its own highly selective transmission and absorption spectral properties, without the need for mechanical structures, in order to provide selective wavelength optical properties instead of angular selectivity properties.

The flowing fluid 60 retains or traps an exceptionally large proportion of the received solar energy as heat, and the resulting highly heated working fluid is directed out of solar trap 50 by way of an outlet passageway, or pipe 70 to a heat storage mass vessel 72 which may contain a porous mass 74, through which hot fluids flow from the solar trap 50 and exit at 75 near ambient temperature. A second heat extraction fluid may enter storage vessel 72 at 76 and exit as a very hot fluid at 78 so that the hot fluidic heat energy may power, on demand from storage, almost any heat engine such as powerplants or other thermal machines 80

In another aspect, the invention is directed to a method for collecting solar energy which may be briefly stated as including the steps of directing radiant energy into a container, or trap, supplying a working fluid to the container, causing the working fluid to have a laminar flow within the container in a direction perpendicular to the entrance aperture surface to nullify conductive and convective thermal losses, employing one or more baffles to nullify internal emission losses, and to convert such solar energy almost totally into thermal energy in order to ultimately heat a working fluid, while preventing almost all internal energy from conductively or radiantly escaping from within the container, and followed by directing the heated fluid out of the container for energy storage or for direct usage.

In another preferred embodiment, many of the subject solar traps may be mounted on a single central tower to be used as dramatically improved central tower receivers in a well known mirror field CSP (Concentrated Solar Power) configuration, such as that illustrated in FIG. 3, wherein sunlight is directed by just a few mirrors (not an entire field of mirrors) to a central tower where one or more flat-panel solar trap receivers may be located. This preferred embodiment will produce several surprising results, including over 900° C. operating temperatures and up to 100-fold reduction in thermal emission losses. Such exceptionally high temperatures and unparalleled high efficiencies, exceeding 90%, create several other surprising results. These include the elimination of thousands of the expensive heliostated mirrors which would have been required by the prior art to make up for massive prior art emission losses, while simultaneously achieving higher CSP powerplant output power and storing much more energy at such higher temperatures for much longer full generating power levels. In other words, grouping small numbers of heliostated mirrors and aiming them at each of a large group of solar traps mounted on one central tower can dramatically increase the power output efficiency of turbines, store dramatically more useful energy, and dramatically reduce the number of costly mirrors in what is normally a field of thousands of mirrors.

Prior art tower receivers attempt to increase efficiencies by employing thousands of mirrors to greatly intensify the solar flux received at a central receiver surface, and by brute force, overcome the well known thermal reradiation losses when producing temperatures of only 600° C. This was illustrated and mathematically shown in the discussion of FIG. 8 to be very inefficient even at temperatures lower than 600° C. (900° K), falling to essentially 0% efficiency at about 900° C. (1200° K).

Note that prior art central towers are designed so that a typical 90 degree wide azimuth angle of mirrors are accepted by a single central receiver hot surface having a typical absorbance of 0.92 and an emissivity of roughly the same 0.9. As will be shown below, a preferred form of the present invention takes advantage of a very narrow solar beam, typically a solid angle of 0.01 to 0.001 steradians (less than 0.3 degrees), as indicated in FIG. 13. Thus, if only about 100 mirrors, in a field of thousands, are aimed at one solar trap 50, then roughly 100 suns can illuminate each of several side-by-side solar traps. Computer controlled mirror heliostats can readily produce many small solid angle (˜0.01 to 0.1 steradian) solar irradiance patterns of about 100 suns per square meter from within a field of thousands of mirrors. Shown in FIG. 13 is just one central tower solar trap example. Many solar traps can be mounted on one central tower, as previously suggested.

The back surface 90 of each solar trap enclosure 54 depicted in FIG. 13 is heated by parallel solar energy that makes it through the one or more illustrated baffles 64. The mechanical baffles may be in the form of honeycombs, screens, or meshes which extend laterally across the enclosure and are substantially parallel to the front surface 56, and which are gradiantly heated from the hot radiant surface 90 and constantly cooled by the counterflowing fluid 60, as indicated by arrows 66, from the region of the front optical window surface 56. The fluid ultimately passes through the highest temperature porous heat exchanging surface 90 and finally exits the solar trap container 52 as a very high temperature working fluid into outlet pipe 70, where it enters a porous thermal energy storage container 72. The hot back surface 90 thermally radiates in a 2π steradian pattern but only a very small percentage of the 2π (6.28) steradians can escape through, for example, a honeycomb baffle which has an approximate 0.01 steradian optical passage. Thus, in this example, approximately 0.01/6.28 or, 1.6% of the total back surface 90 radiation can escape the honeycomb/screen/baffle network 64 and proceed towards the front window surface 56. Using 900° C. (1200° K) as the example working temperature of surface 90, equation 2 predicts a total back surface 90 radiation of ˜117,114 w/m². However, this solar trap example suggests that only about 1.6% of 117,114 watts (or, 1,874 watts) can escape. The startling conclusion is that with 100) suns incident (100,000 watts), only 1,874 watts, or just 1.9% of the incoming solar power from a small group heliostated field mirrors, can escape just one of the several proposed solar traps 50 which can be located on one central tower. Thus, this example of a central tower solar trap array, would be roughly 98.1% efficient at the extraordinary 900° C. collection temperature, compared to approximately 0% prior art central tower efficiencies at 900° C. illustrated in FIG. 8.

As will be further explained below, the term “baffle” applies to more than just mechanical structures such as solid angle constrictor honeycombs (polygons), screens, fibrous wool, and the like. Such mechanical baffles can also be constructed from materials which selectively reflect and absorb solar and infrared radiation. Mechanical baffles can also be coated with selective wavelength materials such as SiO₂.

To be more clear about honeycomb (triangular, square, hexagonal, polygon) mechanical “baffles” and especially “selective wavelength” baffles, equation 4 can help design exceptionally sharp multiple reflection selective wavelength baffles:

Net reflective transmission=(R _(λ))^(n)  Eq. 4.

where: (R_(λ)) defines the decimal reflection of one surface at a given wavelength and n is the number of reflections of light on a path through a selective wavelength baffle

A selective wavelength baffle, such as the baffle 64 used in the embodiment of FIG. 13, transmits almost 100% of parallel incoming sunlight where it undergoes few to no reflections in the baffles on its path to the porous high absorption (hottest) bottom surface 90 of the subject solar trap 50. Grazing angles of solar light incident on the internal surfaces of baffles yield almost total (100%) reflectivity on the incoming path to hot surface 90 However, the 2π emitted radiation from the hot bottom surface 90 to baffle 64 is quite different. Steep angles of incidence from the hot bottom radiation onto the baffle surfaces cause numerous internal baffle surface reflections on the way toward the ambient temperature aperture surface 56. In such multiple reflection conditions, the total transmission of solar wavelength light, according to equation 4, even after ten hypothetical 98% internal reflections, would still yield (0.98)¹⁰ or, 81.7% transmission of solar light to the hottest bottom surface 90. The 18.3% absorbed solar light along the way during the ten reflections, would contribute to slight heating of the thin baffles 64. However, the counterflowing fluid indicated by arrows 66 would absorb that small absorbed solar energy inside the baffles as the fluid migrates from the front to the rear of the container 54, slightly increasing the fluid temperature from its original ambient temperature on its way to the hottest porous bottom 90, where it is greatly heated and exits as a very hot working fluid. In this example it will be assumed that a selective wavelength coating is provided on the baffle walls, which exhibits a slightly absorbing 64% reflection at each longer wavelength than the incoming solar wavelengths. In other words, in this example, the coating is designed to absorb 36% of the radiant long wavelengths that radiate in a 2π steradian pattern away from the hot bottom surface. The bulk of the 2π steradian radiation that hits the baffle surfaces will not only be more absorbed upon incidence of the baffle surfaces, most of the escaping 2π steradian light will also be reflected many more times than the incoming grazing angle solar light. For a brief appreciation of the greatly magnified escaping selective wavelength absorption, merely assume the same number escaping reflections as incoming reflections, namely 10 reflections. In accordance with equation 4, the 10 outgoing reflections (at longer wavelengths) will undergo (R_(λ))^(n) net transmission but this time with R=0.64 and the net transmission would be (0.64)¹⁰, or, only 1.2% net transmission would escape. The vast bulk (98.8%) of the longer wavelength radiation from hot surface 90 would be absorbed in the selective reflective baffle, thereby radiatively heating the baffles, and prevented from escaping. But the absorbed baffle-heat is designed to be removed (cooled) by the much cooler counterflowing fluid 60 headed in the direction toward the hottest bottom of the solar trap 90. Thus, almost all of the far less-absorbed incoming solar wavelength power (1.2%), plus almost all (98.8%) of the intense escaping long wavelength radiation that combine to heat this example's selective wavelength baffle, will be recycled by the counterflowing fluid before the fluid is greatly heated at 90 before it finally escapes the solar trap as a hot working fluid in outlet 70. Equation 4 illustrates the considerable flexibility in designing highly wavelength selective plus angular selective solar traps having very narrow steradian escape paths as well as (R_(λ))^(n) exponentially magnified wavelength selective absorption characteristics.

Even more broadly, the term “baffle,” as employed herein, also applies to selective transmitting and absorbing gaseous or liquid fluids—water and many oils being examples of highly selective transmitters of solar spectrums and highly absorbing infrared absorbing “baffles.” See FIG. 12 for an example of tabulated transmission calculations 49 and absorption spectrum curve for a simple liquid water, highly wavelength-selective “baffle.”

The solar trap system 50 depicted in FIG. 13 illustrates only one profound improvement over prior art CSP central tower receivers. The example demonstrates that there are pronounced improvements possible in powerplant efficiencies at higher temperatures, with far lower cost thermal storage, and dramatic reductions in the number and cost of heliostat mirrors—discussed in more detail below. The FIG. 13 example illustrates more than a 60-fold reduction in radiation losses (only 1,874 watts/m² lost vs. 100,000 incoming watts/m²) compared to near total loss prior art 900° C. central tower receivers. More optimized performance than the exemplary 0.01 steradian system of FIG. 13 is possible. Temperatures far in excess of 1000° C. and over 90% efficiency are believed to be achievable, for there is no known upper temperature limit for counterflowing CSP solar traps. The narrow steradian baffle aperture is a powerful performance tool, but selective wavelength coatings on the proposed honeycomb or baffle surfaces) can further reduce radiation losses. Likewise, various prior art selective wavelength materials and coatings on entry surface 56 can still further reduce radiation losses. Moreover, numerous low emissivity absorber materials, known in the prior art, may be applied to hot surface 90. Finally, wavelength-selective reflective coatings—also well known in the prior art, can be applied to the incoming solar aperture surface 56 to further reduce remnant radiative losses from solar traps. In other words, once the bulk of the prior art inefficiency factors are solved and eliminated by solar traps, there are numerous small improvements still possible, leading up to the statement that solar traps have no known upper performance limits. Clearly, the example in FIG. 13 demonstrates, in broad terms, how to greatly reduce the number of heliostat mirrors—the single largest cost of prior art CSP solar thermal farms, while simultaneously slashing the size and cost of extremely long term thermal storage to create reliable solar power. Counterflowing solar traps make it all possible.

The first priority of counterflowing solar traps is that of maintaining the solar entry surface 56 at non-radiative near ambient temperatures as previously computed in the emission discussion relating to FIG. 8. Counterflow working fluids; that is, fluids flowing counter to the direction of reradiated heat from the trap out of the front entry surface 56, such as nitrogen, argon, neon, krypton, xenon, CO₂, and SF₆, at the correct counterflow velocities, are one key to maintaining the front entry surface at ambient temperatures. Heat cannot convectively or conductively flow against a slow laminar counterflow fluid if the counterflow velocity is equal to or greater than the thermal diffusion velocity.

The curves 100, 102, 104 and 106 in FIGS. 14(a) through 14(d), respectively, illustrate approximate computer plots of thermal diffusion time and velocity parameters (Temperature vs. Distance from bottom surface 90 to entry surface 56) of high-temperature N₂, Ar, SF₆ and Xe gases (not their ambient temperature properties). Plotting these gaseous properties is helpful as part of the calculation to achieve roughly 900° C. solar trap exit gas (working fluid) temperatures with one sun applied. It should be noted that there are no known transparent liquid working fluids capable of withstanding much higher than about 575° C. Thus gaseous fluids are used to achieve very high solar trap temperatures. Reliable high temperature thermal conduction, heat capacity, and other gaseous constants at such high temperatures are required to make thermal diffusion calculations. Common ambient temperature properties cannot produce accurate diffusion answers. However, high temperature gaseous properties are not as precisely documented or readily available in the literature at 1000° K or higher. Thus, the computer modelings here shown are only good first approximations. As a footnote, numerous trace gases such as bromine gas, iodine gas, and SF₆ gas can be non-reactively introduced to counterflowing inert gases to produce desirable selective optical absorbing features to gaseous solar traps to further improve solar energy efficiencies. Thermal properties of gaseous mixtures are even less readily available in published literature.

FIGS. 13 and 14 deserve more detailed explanations. FIG. 14 provides approximate laminar counterflow gas velocities required to nullify thermal conduction (and convection) from the hottest bottom surface 90 to the outermost exposed solar entry surface 56 of the solar trap collector 50. By preventing the solar entry surface temperature from rising above ambient, thermal radiation losses at that surface can be almost eliminated. A second internal radiation would be the direct emitted radiation from the hottest bottom surface 90 directly through the baffle(s) and intercepted by the front surface 56 prior to being thermally radiated into the environment by surface 56. There are several ways to block those internal radiation losses from escaping a solar trap, while simultaneously allowing gases (fluids) to laminarly counterflow. As previously detailed, one good method suggests the use of one or more thin membrane honeycombs having small steradian optical honeycomb apertures. Honeycombs can be constructed of thin foil metals or even thin glass films and shaped to allow free passage of fluids and yet provide only a very narrow solid angle of internal radiation from escaping. Honeycomb surfaces can be highly reflective to parallel incoming solar wavelengths, especially at steep angles of solar incidence from a small group of mirrors, as previously discussed. The same honeycombs can simultaneously highly absorb longer wavelengths of internal thermal radiation light. This represents a selective wavelength option. The combination of narrow steradian beamwidths and the selective wavelength absorption both bar the vast majority of the 2π steradian internal radiation escape. Such mechanical honeycomb radiation blockage prevents thermal conduction, thermal convection, and radiation losses which dominate the potential energy losses. Honeycombs are not the only mechanical means to block internal radiation. Transparent and porous thin films (films with holes), or several thin screens or meshes, can function somewhat like honeycombs to totally block convection and conduction losses in the presence of a counterflowing working fluid. Similarly, extremely thin wire screens or fibers can also pass almost all of the incoming sunlight, absorb infrared, and permit counterflowing fluids. All of these options are herein broadly called mechanical “baffles.”

Another advantage of counterflowing fluids is the continuous cooling effects on the fluid-cooled baffle surfaces. Radiation, which is so T⁴ dependant, can be largely kept in check by the cooler counterflowing fluid. In other words, the highest temperatures nearest the bottom surface 90 and the associated extraordinarily intense radiation therefrom, is absorbed deep in the honeycomb where that heat is re-absorbed and convectively carried by the counterflowing fluid deeper into the trap 50 towards surface 90. When the correct fluid velocity is employed, the end result is a fixed thermal standing wave between the ambient entry surface 56 and the bottom hottest surface 90.

Still another advantage of counterflowing fluids in a solar trap is that they can be employed as the working fluid throughout the entire solar collector and its thermal storage container, shown at 72 in FIG. 13.

Referring to FIG. 13, the counterflowing fluid 60 forms a loop through the solar trap system 50. Ambient temperature fluid 60 is introduced at inlet pipe 62 immediately behind, at the side of, and substantially parallel to the solar entry surface window 56. The window can be a thin transparent glass or even a thin UV absorbing plastic membrane because it is always maintained near ambient temperatures. The ambient fluid slowly counterflows toward bottom 90 of the solar trap container 54, and this “working fluid” then exits the solar trap container 54 at high temperatures through pipe 70, which conveys it to the top of the high mass 74, porous solar storage container 72. The porous thermal storage mass 74 can be glass beads or simply low cost SiO₂ sand or rocks—materials which are capable of withstanding ˜1650° C. (3000° F.). The working fluid heats the porous thermal storage bed to its highest temperature near the top of the bed and then exits the bottom of the thermal bed, at almost ambient temperature, into pipe 62 for recirculation through the system 50, again at nearly ambient temperatures. The bottom of the thermal mass bed would eventually rise in temperature were it not for a second counterflowing heat extraction loop 77 incorporating embedded heat exchanger tubes 75 inside the storage bed, as shown in FIG. 13. This counterflow heat extraction” loop produces the highest temperature exit fluids or hot gases, that may be used, for example, to supply heat to the boilers of an efficient powerplant 80 or some other thermal machine, whereafter the heat exchange fluid can be returned, at near ambient temperature to the thermal storage bed at 76

As is well known by those skilled in powerplant technology, river water or some other means is needed to keep powerplant turbine condensers as cool as possible in order to meet equation 1 Carnot efficiency requirements. Thus, the exiting working fluid from a powerplant (or other thermal machine) can be returned to the bottom of the thermal storage bed 72 by way of loop 77 return pipe 76 at or near ambient temperatures. The bottom of a counterflowing storage bed can be maintained at ambient temperatures while the top portion of the bed can be maintained at the highest possible temperatures from the solar trap. Should the collected solar energy be excessive and saturate the entire solar storage medium, several fail-safe features can automatically limit and protect the solar trap. For example, if the working fluid were returned to the solar entry surface at roughly 90 to 100° C., the front surface 56 of the solar trap will radiate and lose about 1000 watts/m², an amount equal to the most intense incoming solar energy. Thus, solar trap collection can be self limiting. The counterflowing fluid 60 can also be halted or slowed, thereby also limiting the collection of solar energy. Finally, if snow starts to build on top of solar traps, the counterflowing fluid temperature can be briefly increased to melt the snow with a surprisingly small amount of stored energy, thereby preventing snow accumulation. The thermal energy to melt snow (80 calories/gram) is not a large drain on a well designed solar storage system.

The counterflowing working fluids 60 can be selected from a wide variety of gases/fluids. The preferred gases, but by no means limited to these gases, are the inert gases such as N₂, Ar, Ne, CO₂, SF₆, Kr, Xe, or mixtures thereof, with or without selective absorbing spectral gas additives. Some would argue that SF₆ gas is a potent global warming greenhouse gas and should not be industrially used. However, the very purpose of solar energy is to eliminate gigatons of CO₂ greenhouse emission gases. Thus, employing a small charge of a very potent greenhouse gas has the profound effect of eliminating millions of times of combustion greenhouse gas emissions. SF₆ is fully justified in all solar trap configurations proposed herein. Xenon is another controversial gas. Xenon, which has no greenhouse impacts, is a very rare and expensive gas. Nonetheless, Xe is one of the best gases to use in solar traps and the cost savings of physically smaller solar trap systems can offset the one-time cost of expensive Xe gas. Over 10 million liters of Xe gas is currently a byproduct of air separation technologies in producing mostly liquid nitrogen and oxygen. Low purity Xenon could, in principal, be practically given away while negligibly impacting LN2 and oxygen revenues. Xenon atmospheric concentrations are about 87 parts per billion (about 4.3×10¹¹ kg in earth's atmosphere or, about 76 billion cubic meters—far more than needed to solar power civilization). Similar arguments can be made in favor of employing 10 times more abundant and 10-fold less expensive krypton or mixtures of Kr and Xe.

Solar traps used as receivers in central tower (CSP) systems offer additional indirect performance advantages. As previously stated, the first large advantage includes the possibility of more power output from a powerplant as a result of higher Carnot operating turbine temperatures. The highest turbine powerplant efficiencies (over 60%) are presently possible in state-of-the-art 760° C. (1400 F) ultra critical steam temperature powerplants. Compare that efficiency with just over 35% efficiencies of most of the world's current coal burning powerplants. Such high solar operating temperatures can almost halve the number and cost of CSP mirror fields—while providing much higher thermal storage temperatures. Recall that storage temperatures drop when called into service and thus, ideally, much higher storage temperatures can maintain full powerplant efficiencies. Very high CSP solar trap efficiencies make capturing and storing extremely high temperatures possible, which slashes the number of field mirrors by more than 50%. And the cost of thermal storage can also be reduced dramatically in surprising ways. Thus, the employment of the subject gaseous solar trap embodiment can reduce the cost of CSP electricity more than 3 to 5 fold. That helps to make solar electricity even more competitive than the least expensive electricity on earth—even before financially accounting for the far cleaner land, air, and sea environments.

Thus far, only one CSP preferred embodiment of the subject invention has been illustrated. Another, non-CSP embodiment of the invention has an even greater impact by totally eliminating heliostated concentrating mirrors. The embodiment of the invention depicted in FIG. 13, illustrating up to ˜100-suns, counterflowing gases, selective absorption, and angular geometric mechanical radiation baffling, can also be applied to one-sun flat panels on land or on commercial building rooftops such as office, industrial, and shopping mall rooftops, and even on commercial parking lots. Such flat panel solar traps only collect one-sun (1000 watts/m²) not 100,000 watts/m² as in the above CSP solar mirror farms. But, flat panel one-sun collectors do not suffer from mirror shadows 13 between heliostated mirrors. Therefore, flat panel collectors have the advantage of collecting roughly 3 to 4 times more solar energy per acre compared to costly mirror fields.

No sacrificial solar land is required if flat panel solar traps are located on existing rooftops and atop existing parking lot land. In just the U.S., there exist about 7,000 square miles (18 billion sq meters) of potential solar rooftops and solar parking lots. At high noon, 18 billion m² of sunshine equates to about 18,000 gigawatts of solar power (˜30 trillion kwhrs per year of cloudless skies . . . about $3 trillion at $0.10/kwh). 30 trillion kwhrs equates to about 100 quads (100 quadrillion BTUs) per year or, the total U.S. energy demand of all electricity, liquid fuels, natural gas, and nuclear energy combined. Of course, this first approximation assumed cloudless days. But even with normal cloud coverage plus large energy storage, the total actual clean energy available on rooftops and parking lots would provide a very large fraction of the total U.S. energy demands.

With emphasis, this flat panel, one-sun embodiment illustrates the broad applications of the subject invention, inviting the use of a wide range of materials, working fluid choices, and geometric configurations, to increase temperatures and optimize solar trap performance. Estimates have shown that the retail value of solar energy which can be collected and sold from shopping center rooftops (as space heating, cooling and electricity) can exceed the typical rental revenues that can be generated by mall owners under shopping mall roofs.

The key to one-sun, flat panel solar trap performance remains similar to 100-sun CSP solar receiver operations. In other words, a one-sun solar trap can achieve the same 98% efficiency if only 20 watts/m² of the available 1000 watts/m² were lost (instead of 1,845 watts/m² of 117,000 radiative watts at 900° C.). See the FIG. 13, small-mirror groups (narrow collection angles) and 100-sun calculations. Thus, the similar solar trap assumptions previously made for 100-suns, but with just one sun applied, can produce a similar 98% efficiency if the maximum temperature achieved were reduced from 900° C. (1200° K) to about 400° C. to about 500° C. (>700° K, 752° F.). The dominant T⁴ feature of radiation governs the maximum temperature achievable, given the same 0.01 steradian baffle assumptions. However, if only 90% (not 98%) one-sun efficiency is acceptable, the maximum radiation loss allowed would be 10% of 1000 w/m² or, a 100 watt loss in the FIG. 13 embodiment would occur at about 700° C. (1000° K, 1290° F.). Thus, a 90% efficient one-sun. 700° C. flat panel solar trap is readily achievable, given the many additional prior art enhancementa previous listed (low emissivity materials, selective wavelength reflector, etc) without the need of any costly heliostated concentrating mirrors. And, one-sun flat panel solar traps only require roughly ⅓ to ¼ as much solar collection acreage because flat panels can be located side by side with little to no shadows cast between them.

One-sun flat panel solar traps can be gas filled or liquid filled for counterflow purposes. Few optically clear room temperature liquids can withstand prolonged exposure to much more than 500° C. (800° K, 932° F.), whereas many gases can withstand prolonged exposure to more than 10,000° C. One optically clear liquid which boils at about 575° C. is a common vacuum diffusion pump silicon oil known as 1,1,3,5,5-pentaphenyl-1,3,5-trimethyl-siloxane oil. Very thin (centimeters thick) flat panel solar traps of the subject invention can work with silicone oils, but even higher temperatures can be trapped using inert gases, particularly high atomic weight Xenon gas. A thin, “flat panel” solar trap is illustrated in its simplest form at 120 in FIG. 15. Such Xenon gas filled solar traps can be thin, extremely lightweight, and achieve very high temperatures and very high efficiencies. See FIGS. 3 and 14 for thermal diffusivity calculations of Xenon and Silicone oils which were computer generated using equation 3. Notice the divisor term “X²” in equation 3, where X is the thermal propagation distance (in meters). That means that the propagation time exponentially increases by the square of the propagation length or, in this case, by the thickness of the working fluid. Note also that the thermal propagation time (in seconds) and the propagation distance (in meters) yields a velocity of heat propagation in meters/second. That propagation velocity is the first of two values to be calculated in order to build a solar trap having an equal but opposite counterflowing velocity to completely nullify the thermal diffusivity of a fluid.

Once a thermal diffusion velocity is computed for a given fluid, and under high temperature conditions (where all of the fluid properties, such as density and thermal conductivity, change with temperature), a second calculation can be performed knowing the input solar energy per second. In the Xenon flat panel solar trap example of FIG. 15, the solar input power of one-sun, illustrated as arrows 122, is directed onto a solar entry surface 124 of a container, or receiver 126, which may be in the form of a rectangular box having a bottom wall 128 and side walls 130. The solar trap receiver 126 may incorporate one or more fine wire screens, illustrated at 132 and 134, plus one or more small steradian honeycomb baffles 136 and 138, extending across the solar trap parallel to and spaced below the entry surface 124. A working fluid 140 is supplied to the receiver 126 at the top of wall 130 in a direction parallel to the front entry surface 124, and flows downwardly through the receiver, and through the screens and baffles, toward the bottom wall 128, as illustrated by arrows 142. Within the solar trap receiver 126 and spaced above the bottom wall 128 is a solar spectrum absorption black porous layer 144 which provides an exit plenum 146 which allows the heated working fluid to flow out of the solar trap receiver, as indicated by arrow 148 to flow to a suitable storage unit, such as unit 172 illustrated in FIG. 13, or to a suitable thermal machine.

The solar input power 122 to a flat solar trap receiver 120 may be assumed as 1000 watts/m² or 1 kj/sec. To achieve the highest solar trap operating temperature a sufficiently high fluid thickness, X (Eq. 3), and a sufficiently slow counterflow velocity must be selected so as to obtain the longest possible solar exposure time in order to heat the fluid to the desired temperature before it exits the solar trap. The latter calculation simply requires knowledge of the exposure time (which is determined by the solar trap thickness; i.e., the distance between the entry surface 124 and the black porous layer 144, and the fluid velocity) and having access to the density and the specific heat values of the chosen fluid at the desired high operating temperature. These are reasonably straightforward calculations done by those skilled in these arts, using equation 3, plus the fluid thermal constant values, such as specific heat values, at elevated temperatures. The latter calculations have been performed for Xenon gas exiting at 900° C. and it was found that a Xenon solar trap must be about 15 cm thick and must counterflow inside the trap at a velocity of about 0.75 cm/second under a one-sun exposure intensity. See FIG. 14(d).

Higher temperatures can be achieved if the exemplar Xenon solar trap is made thicker than 15 cm and thus, the counterflow velocity slowed considerably (by “1/X²”). As illustrated in FIG. 15, once thermal diffusion is nullified, as indicated by arrow 160, by the ambient temperature counterflowing fluid 140, and the solar energy entry surface 124 radiation losses are minimized, the only large remaining thermal radiation loss, which must also be minimized, is the intense 2π thermal radiation losses from deep within the solar trap, indicated by arrows 170 emanating from the high temperature region of bottom black porous surface 144. The latter radiation losses can be minimized by employing the host of angle selective mechanical and wavelength-selective baffles 132, 134, 136, and 138 previously discussed, which in combination are able to achieve almost any degree of radiative re-absorption and counterflow-recycling of thermal energy desired, leaving only a very small quantity of radiation to escape, as indicated at 180. This is why it was previously stated that the subject solar traps have no known upper temperature limits with just one-sun (or less) applied, and even more so if a small group of highly collimated CSP mirror optics are also employed with solar trap receivers. Moreover, it is unnecessary to remind those skilled in these arts that even higher solar trap temperatures can be achieved by employing well known low emissivity materials for absorbing surface 144; high infrared absorbing thin films on the inner surfaces of honeycombs (as previously stated); and even employing well known wavelength-selective entrance optical windows at 124, which can be coated with infrared reflective materials—all well known in the prior art. Thus, in addition to the yet unknown upper temperature limits of the subject very high temperature counterflowing solar trap invention, the temperature and efficiency limits can be pushed even higher by employing a variety of well known prior art absorption and reflection techniques.

As illustrated in FIG. 16, it is anticipated that thousands of existing coal powerplant or other sources of steam 190 can be retrofitted with very high temperature, thick, gas filled, flat panel, solar traps 192, to provide a clean solar-steam-generating source of power via outlet line, or conduit 194. In the example of this figure, steam from source 190 is conventionally supplied to drive a powerplant turbine 196 to drive a generator 198, with the condensed steam being returned by way of line 200 and heat exchanger 202 to the be reheated at 190. The solar trap 192 may be connected into the conventional system by directing the output fluid from the heat exchange 202 via line 204 to be circulated through the solar trap, as described above with respect to FIG. 15, where it is heated and supplied to the steam generator 190. As illustrated, the return line 200 is broken at 206 to direct the fluid to the solar trap. This arrangement, which requires no costly heliostated mirror fields, provides a simplified solar energy retrofit of a conventional combustion powerplant. The main retrofit requirement is enough flat panel solar trap acreage—about 1,000,000 square meters (˜0.4 square mile, 250 acres) per gigawatt of cloudless solar collection, plus a heat exchanger 202 and a sufficiently large thermal storage field to accommodate the longest sustained cloud coverage in the selected geographic location. But since coal fuel represents, by far, the greatest long term powerplant operating cost, the cost of a one time solar retrofit is dwarfed by the cost of coal over the lifespan of a coal powerplant, not counting the numerous other financial and environmental benefits of solar energy retrofitting.

Also shown in FIG. 16 at 210 is an optional non-powerplant solar energy application; namely, that of district or city-wide space heating and space cooling which employs the system described in U.S. Pat. No. 6,688,129; namely, a nearly free thermal energy delivery technology which employs the existing underground potable water infrastructure to deliver nearly unlimited solar powered ice-cold potable water in summer months or, solar pre-warmed potable water in winter months.

High temperature commercial and industrial rooftop solar raps discussed above can be scaled down for use on residential rooftops, which represent many thousands of square miles of solar surface area in the U.S. Furthermore, residential solar traps applications offer several unexpected benefits far beyond those provided by prior art supplemental hot water rooftop technology. FIG. 7, discussed above, also depicts the shortcomings of such prior art solar rooftop heaters. The ability of solar traps to collect at hundreds of degrees higher temperatures, allows tens of times more useful energy storage, not just for supplemental hot water but, for total hot water, total space heating, total space cooling, and total residential electric demands as well.

A typical 150 m² residential rooftop can collect up to 1000 watts/m for 5 or more hours per day or, about 750 kwhrs (2.55 million BTUs) per day (930 million BTUs/year). Even if such a typical residence needed 30,000 BTUs/hr (8.8 kw/hr) of winter space heating (720,000 BTUs per day), there would be 1.85 million extra BTUs per day left for hot water (typically 100,000 BTUs/day) and electricity (2 kwhrs×24 hrs=48 kwhrs, or 163,000 BTUs per day)—leaving about 1.567 million BTUs/day for sale during winter months if there were a way to sell the excess solar energy at each residence. In this example, the total 2.55 million BTUs/day or, 930 million BTUs/year, annual rooftop energy, based on a current retail energy price of about $4 per 140,000 BTUs, would be worth about $26,592 per year. Just the excess 1.567 million BTUs per hour (572 million BTUs/year) rooftop energy would be currently retail valued at about $16,118 per year, if a way to sell the excess thermal rooftop energy was available. There are at least two ways that excess residential energy can be sold. One obvious high temperature option would be to generate electricity on site and sell the electricity using the existing power lines feeding the building. If, for example, a mere 25% efficient turbine generator produced 25%×572 million BTUs per year of electricity—or 167,637 kwhrs/year—the electricity might be valued at 10 cents/kwhr, and the excess electricity alone would be worth $16,764 and the waste heat (429 million BTUs) from the 25% efficient generator, would have an additional value of $12,257—a total excess energy sale potential of $16,764 plus $12, 257 (or, $29,021/year)—again, provided a means to sell the waste heat existed.

U.S. Pat. No. 6,688,129 discloses a means to sell such waste heat. The patent describes an exceptionally low-cost method to distribute either pre-warmed or pre-cooled potable water using the existing potable water lines feeding residential buildings. And if high temperature residential rooftop units are partially used to generate on site electricity, not only can the excess electricity be sold using the existing power grid, but the inefficient waste heat from miniature residential thermoelectric power generators can be employed on site for residential heating, and the excess thermoelectric waste heat can also be sold using the nation's existing potable water infrastructure. There is possible a nearly 100% efficient use of residential solar energy. Almost all of the solar collected heat can go towards generating electricity (which can all be sold at the highest prices), and the remaining waste heat can be used for winter space heat and to provide for hot water on site in the solar residence. Solar heat beyond the needs of the on site solar residence can be sold as warm potable water to heat nearby buildings as detailed in U.S. Pat. No. 6,688,129. In summer months, super efficient, high temperature, solar traps are ideal for highly efficient heat-powered, prior art, Absorption Cooling technology. Excess ice-cold space cooling water can be sold via the existing national potable water infrastructure.

FIG. 17 illustrates at 220 a serpentine counterflow embodiment of the subject invention, generally indicted at 220, which employs an indirect, serpentine counterflow geometry. In the embodiments of FIGS. 13 and 15, the counterflowing fluid travels from the solar entrance surfaces 56 and 124, respectively, in a substantially perpendicular direction toward the respective hottest bottom surfaces 90 and 144, and exits as a hot working fluid. In this embodiment, a working fluid 222 enters a receiver, or chamber 224 having a serpentine fluid flow that is substantially parallel to a solar entry surface 226. This path is defined by a series of thin transparent walls or baffles 230 extending substantially across the width of the chamber but open at alternate ends to define a series of pathways 232 to provide a serpentine flow path for the fluid though the length of the chamber from the entry surface 226 to a solar spectrum absorbing final black wall 240, as indicated by arrows 234. The thin transparent baffles 230 not only define the serpentine flow path of the fluid through the receiver, but also preferably is a glass or a film that exhibits an index of refraction almost exactly the same as the working fluid flowing through the solar trap 220. The working fluid velocity is highest in the first serpentine cavity 242 in contact with the solar entry surface 226 and slowest in the last serpentine chamber 244 of the solar trap. Thus, the solar entry surface is maintained at the coolest temperature, near ambient, as in pervious solar trap embodiments. The working fluid 222 undergoes a “U” turn at the end of each serpentine layer of flow, as shown by the arrows 234, and it continues its serpentine flow through the receiver chamber toward the hottest end 244 before the working fluid exits at 250. With index matching, there would be almost zero reflection losses inside of the entire solar trap, and all of the entering solar spectrum can be absorbed partially in the transparent counterflowing fluid or, better-still, fully absorbed in serpentine chamber at 240 prior to exiting at 250, as a very hot fluid, to a thermal storage mass (not shown). If the chosen counterflow serpentine fluid is water based, the upper temperature limit of the nearly 100% efficient solar trap, obviously would be less than about 50° C. But, as previously suggested, many other higher boiling point liquids, including silicon or hydrocarbon oils, which exhibit spectral properties similar to water, can achieve nearly 100% solar collection efficiencies at unparalleled temperatures up to about 550° C. (˜850° K, 1022° F.). Such extreme one-sun solar collection efficiencies, with almost no thermal energy losses, allow physical thermal storage vessels to be 10-100 times smaller, while also providing extreme longevity thermal drawdown times. The combination of low-cost super efficient high temperature collection plus dramatically lower cost storage, is unparalleled in solar history.

Since transparent liquid fluids greatly limit the operating temperature of the subject solar trap invention to less than about 550° C., unlimited temperature gas fluids can be employed in the serpentine counterflow solar trap to achieve the highest operating temperatures. However, gas fluids do not offer optical index matching opportunities as do transparent liquids. Fortunately, slightly absorbing, extremely broad band thin films can be coated on each transparent serpentine layer 230 to nearly eliminate all reflections within a serpentine solar trap. Such slightly infrared absorbing layers 230 and absorbing thin films offer additional benefits to trapping thermal radiation as well. Beer's law and equation 4 come into play here, as discussed previously concerning selective wavelength baffling, and as depicted in FIG. 12 concerning the selective transmission properties of water. Thus, instead of liquid serpentine solar traps, gaseous serpentine traps can achieve much higher operating temperatures, limited only by the endurance of materials. The ambient temperature entrance side of serpentine solar traps is always much cooler than the hottest end near surface 240. Thus, it is obvious from previous discussions that extremely high temperature transparent windows, such as fused silica glass or even optically transparent screens can be employed at the hottest end of serpentine solar traps. In fact, it has been made clear in other embodiments of the subject invention, that screens, windows, honeycombs, can be combined without departing from the general counterflow embodiments—all aiming to maintain the entrance surface at near ambient temperatures.

The diagrammatic serpentine flow illustrated in the embodiment of FIG. 17 does not have to provide smoothly “layered” or “paneled” flowing fluids. Instead, in another embodiment of the invention diagrammatically illustrated in FIG. 18, a solar trap chamber 260 may incorporate a series of layers of serpentine pipes, or channels 262 carrying fluids depicted by arrows 264, without departing from the general serpentine counterflow concept. FIG. 18 illustrates a windowless front solar entry portal generally indicated at 266, with only four layers of varying diameter and varying spaced solar-absorbing pipes 268, 270, 272, and 274. The counterflowing liquid or gas enters the smallest diameter pipes, at entrance 280, traveling at the highest velocity, which maintains the solar entry pipe layer 268 at or near ambient temperature, and thereafter flows at slower velocities through the larger pipes until it reaches the hottest pipes 274 before exiting as a working fluid at portal 282 before entering a thermal storage mass (not shown).

A serpentine counterflow solar trap offers all of the high solar spectrum entry opportunities of other solar traps detailed herein, including the elimination of thermal diffusion and entry surface thermal radiation losses; including the ability to re-absorb and recycle intense internal thermal radiation; and the opportunity to achieve exceptionally high solar trapping efficiencies at exceptionally high efficiencies. Therefore, such high temperatures at high efficiencies, offers the same opportunities to long-term densely store solar thermal energy at the lowest cost for reliable on-demand solar energy for unlimited applications.

Low velocity counterflowing liquid and gaseous working fluids in the subject solar trap invention have been illustrated to totally nullify thermal conductivity, thereby eliminating almost all front solar entry surface radiation losses in solar thermal collection technology. Wavelength selective and mechanical angular selectivity blockage of internal hot surface radiation has also been shown to prevent thermal radiation from escaping the subject thermal solar traps. The combined results of the breakthrough solar trap technology plus much lower cost energy storage enables many times less expensive solar power, thereby enabling worldwide implementation of the most abundant energy resource on earth as the least expensive and cleanest energy on earth. Quad generation, the world's most efficient use of energy for electrical power, space heating, cooling, and hot water is also disclosed.

Several very high temperature preferred embodiments of the subject invention illustrate how it can dramatically improve existing central tower CSP technology; how it can retrofit existing combustion and nuclear powerplants with clean, reliable, high temperature solar energy; and how solar energy technology can rapidly progress beyond the concept of large central power utilities by implementing small, highly profitable distributed rooftop solar energy. And it has been shown that distributed rooftop solar technology can meet the energy needs of entire nations without demanding any dedicated solar land. High temperature solar collection has been shown to economically store vastly higher useful solar energy for as long as desired, thereby making solar energy reliable without the need for extremely costly standby conventional backup power.

It has also been shown how potable water U.S. Pat. No. 6,688,129 can be an integral component in delivering vast quantities of perfectly clean and cheap solar energy to buildings, and at incredibly low delivery costs, for space heating, cooling, and hot water—over of the world's energy demand. Likewise, it has been shown how low-cost distributed solar electricity generation can employ the existing grids to power nations, especially if ultra efficient electric cars are popularized.

Solar energy not only can, but must, become the world's least expensive energy resource. There is no larger, cleaner or, better option. The subject invention can more than meet that need. It offers an unparalleled boost to prosperity. And, to the more conscientious people, the most important consequence of a rapid transition to a solar age, are the free environmental bonuses and the preservation of the world's versatile and finite hydrocarbon resources for posterity. Mankind can finally stop excavating for energy and stop burning our valuable resources.

Thus, it will be understood by those skilled in the several arts described herein that the subject invention and its many described embodiments and numerous variations may employ a wide variety of mechanical structures and numerous transparent and semi-transparent liquids and gaseous fluids to produce a counterflowing effect, wherein a working fluid opposes thermal conduction, thermal convection, and/or internal reradiation effects, to reduce energy loss to near zero, and thereby increase solar energy collection efficiency, without departing from the spirit and scope of the invention, as set forth in the following claims. It will be understood that the upper temperature limits discussed herein are by no means the maximum temperatures or the maximum solar efficiencies achievable by the subject invention and that an unlimited combination of spectrally selective solids, liquids, gases, and coatings can be employed in and with counterflowing working fluids and, in general, to “baffles” for higher performance solar traps, without departing from the spirit of the subject invention. 

1. An exceptionally high efficiency, high temperature; solar energy collector, comprising: an enclosure having a front portion and a rear portion; a solar entrance at said front portion to allow incoming solar radiation to enter said enclosure; a fluid inlet at said front portion of said enclosure to receive a counterflowing working fluid at substantially ambient temperatures; at least one baffle positioned laterally across said enclosure between said front and rear portions to guide the flow of said fluid through said enclosure toward said rear portion, said at least one baffle allowing said incoming radiation to be nearly fully absorbed and converted to heat within said enclosure; a fluid exit at said rear portion, wherein said at least one baffle further preventing radiation which is generated within the enclosure from escaping, whereby the fluid is heated and exits the enclosure at said fluid exit as a highly heated working fluid.
 2. The energy collector of claim 1, further comprising a solar spectrum absorption surface within the said enclosure, wherein said baffle permits an effective passage of said counterflowing fluid between said solar entrance surface and said absorption surface.
 3. The energy collector of claim 2, further comprising a plurality of baffles within said enclosure, each said baffle being gradually heated by reradiated and conductive energy within said enclosure and by incoming solar energy, as said working fluid flows from said front portion of the enclosure where it is at ambient temperature, toward said rear portion, whereby said fluid exits the enclosure as a very high temperature working fluid.
 4. The energy collector of claim 3, wherein said solar incoming radiation heats said fluid, said baffles, and said rear portion, wherein said heated fluid and heated baffles reradiate energy, and wherein each baffle is fabricated of, or is coated by, a material which exhibits selective wavelength absorption, whereby solar radiation passes through said baffle toward said rear portion and reradiated energy is substantially prevented from reaching said front surface.
 5. The energy collector of claim 3, wherein said baffles are honeycombs which exhibit angular selectivity to impinging radiation, wherein said incoming solar radiation heats said fluid, said baffles, and said rear portion and any reradiated energy from said heated fluid, said heated baffles, or said rear portion is substantially prevented from reaching said front portion.
 6. The energy collector of claim 1, wherein said at least one baffle produces substantially laminar fluid flow in said enclosure in a direction that is substantially perpendicular to the direction of said incoming solar radiation and also follows a serpentine counterflow path from said front portion to said rear portion.
 7. The energy collector of claim 6, wherein said at least one baffle is nonporous and transparent to incoming radiation and exhibits an index of refraction substantially the same as the working fluid flowing through the enclosure.
 8. The energy collector of claim 7, further comprising a plurality of baffles in said enclosure to produce said serpentine path, wherein said incoming radiation is solar energy to heat said fluid and said rear portion, wherein said heated fluid and said heated rear portion reradiate energy, and wherein each baffle exhibits selective wavelength absorption, whereby solar radiation passes through said baffles toward said rear portion and reradiated energy is substantially prevented from reaching said front surface.
 9. The energy collector of claim 1, wherein the rear portion of said enclosure incorporates a solar spectrum absorber.
 10. The energy collector of claim 8, wherein said solar entrance includes a transparent aperture for admitting said solar radiation.
 11. The energy collector of claim 1, wherein said solar entrance includes a transparent aperture for admitting said solar radiation.
 12. A method for collecting solar radiant energy, comprising the steps of: directing solar radiant energy through a front portion of an enclosure toward a solar spectral absorbing rear portion of the enclosure to trap heat in the enclosure; supplying a counterflowing working fluid to said enclosure at a relatively low temperature; causing said fluid to flow generally away from said front portion of the enclosure toward said rear portion of the enclosure to be heated by absorbed incoming solar radiant energy in said absorbing rear portion; preventing heat from within said enclosure from exiting said enclosure while the fluid is still within said enclosure; and directing heated fluid out of said enclosure.
 13. The method of claim 12, further including causing the working fluid to have a substantially laminar flow within said enclosure in a direction generally perpendicularly away from said front portion.
 14. The method of claim 12, wherein the step of preventing heat from within the enclosure from exiting includes wavelength-selectivity.
 15. The method of claim 12, wherein the step of preventing heat from within the enclosure from exiting includes angular-selectivity.
 16. The method of claim 12, further including thermally insulating the enclosure.
 17. The method of claim 12, wherein causing said fluid to flow generally away from said front portion of the enclosure toward said rear portion of the enclosure includes providing a plurality of wavelength selective or angle selective baffles.
 18. The method of claim 12, wherein causing said fluid to flow generally away from said front portion of the enclosure toward said rear portion of the enclosure includes a plurality of flow-direction baffles extending across said enclosure.
 19. The method for making a solar energy collector, comprising the steps of: providing an enclosure having a front portion and a rear portion; providing a solar entrance at said front portion to allow incoming solar radiation to enter said enclosure; providing a fluid inlet at said front portion of said enclosure to receive a counterflowing working fluid at substantially ambient temperatures; providing at least one baffle positioned laterally across said enclosure between said front and rear portions to guide the flow of said fluid through said enclosure toward said rear portion, said at least one baffle allowing said incoming radiation to be nearly fully absorbed and converted to heat within said enclosure; and providing a fluid exit at said rear portion, wherein said at least one baffle further preventing radiation which is generated within the enclosure from escaping, whereby the fluid is heated and exits the enclosure at said fluid exit as a heated working fluid.
 20. The method of claim 19, wherein said baffles are honeycombs which exhibit angular selectivity to impinging radiation. 